The present invention relates to an image forming apparatus capable of editing a color image based on a designated color in a polychromatic original image.
There has been known a copying machine capable of editing a picture image by trimming or masking a specific area of an original image or moving it to another position. A copying machine, disclosed for example in Japanese Laid-open Patent Publication No. 60-239764, is also known which includes a plurality of developing devices and produces a copy of a specific area of an original image in a designated color using the developing device for that color.
These copying machines are all of the type in which a specific area of an original image is designated and image editing is performed for that specific area, but none of these prior art copying machines is able to have a specific color designated and perform image editing corresponding to that designated color.
More particularly, these copying machines are unable to perform such operations as to erase part of an original image in a specific color, to erase other parts of the image than that in a specific color, or to convert part of the image in a specific color into that in another color.
With a digital copying machine, such operations are performed as to electrically read a color image of an original by means of an image reader formed of a scanner and the like, with the image separated into those of three colors, red (R), green (G), and blue (B), to convert the obtained image data into image signals for each of three developing colors, for example cyan, magenta, and yellow, to form images according to the image signals for each of these colors, and to combine these images to obtain a color image.
When performing color image editing with such a digital copying machine, a means becomes necessary which will specify a desired color for performing the image editing of the image data read out by the image reader. As means for specifying the color, such a means can be considered which will specify values of density for each of the developing colors, cyan, magenta, and yellow, but there is a problem that specifying colors by numerical values is not a simple matter and also is liable to cause an error in the specified color.